Once upon a time some friends and I reasoned this one out.

First all the guys observed that it was stupid carrying around a condom in their wallet at all times hoping to get laid for two main reasons.
Zero: Latex degrades when it is kept in a hot place such as a back pocket.
One: You look like a dork when you pull out your wallet to pay for something and there is a big condom ring in it.

However, guys are willing to ignore such problems as above for the mere possibility that they might get some. Besides it is in the interest of safe sex.

Now being the kind of people that think outside the box we pondered how to insure maximum get some potential and solve the above mentioned problems. We came to this solution:

The woman should carry the condoms!!! in her purse whenever she thinks there is a possibility of some nookie.

This does not lower the get some potential, because in the end she is the one who will determine whether there will be any action on a given evening no matter who carries the condoms.

It does, however solve the above two problems. A purse is a fine place to store condoms, and there is plenty of room for them in there.

Now after this wonderful paradigm shift the guys began wondering what they should carry on the date, I mean after carrying condoms for so long their wallets would seem empty. So ultimately we solved this as well.

A guy should carry a Moist Towelette in his wallet!

It is good for cleaning up messes. No matter if he gets a chance to make a mess with the female or if he has to make a mess by himself after the date it is still a useful thing to have.

Known Problems with this theory:
one has to explain it to the woman. Some are very practical and level headed and understand the sound reasoning behind it and others do not.
I am unsure exactly how this applies in homosexual relationships.
We have WAY too much free time on our hands for even coming up with this.